Raimonds Valdmanis

University of Latvia | LU · Institute of Physics

To promote more efficient use of local renewable energy resources for heat production, an original pilot device has been created with a maximum heat power of 20 kW for combustion of different origin biomass pellets (forestry and agriculture residues). For the improvement of the processes developing downstream of the device, the preliminary heating...

Original experimental device with heat output up to 20 kW was developed and tested with the aim to provide wider use of the locally available renewable energy resources - agriculture residues (wheat straw) for sustainable energy production and reduced effect of energy production on climate changes. To provide efficient control of thermochemical con...

In this paper, the thermochemical conversion of selectively pre-treated binary blends composed of 30% microwave (MW) pre-treated biomass pellets (wheat straw, wood) and 70% of different origin raw biomass pellets (wheat straw, wood, or peat) was performed using originally developed experimental device with a heat output up to 20 kW. Biomass pellets...

In the present study analysis of co-firing microwave (MW) pre-treated biomass pellets of different origins (wood and wheat straw), with raw pellets (wood, straw, and peat), to control and improve thermochemical conversion of biomass blends and achieve a sustainable use of local energy resources in energy production has been carried out. Effects of...

Possibilities of more efficient use of regional lignocellulosic resources (wood, wheat straw, peat) of different origin for an environmentally friendly energy production using selectively MW pre-treated blends of commercial wood or wheat straw pellets with raw peat pellets are studied. A hypothesis is proposed and tested that selective MW pre-treat...

The main objective of research is to promote wider use of the regional bioenergy resources for the development of environmentally friendly energy production providing microwave pre-treatment of different origin lignocellulosic biomass pellets (wood, straw, and peat) at frequency 2.45 GHz. A hypothesis is proposed and tested that MW pre-treatment of...

The objective of the study was to investigate a more effective use of commercially available biomass pellets (wheat straw, wood, peat) using microwave pretreatment to improve heat production. Pellets were pretreated using the originally designed microwave torrefaction device. The effects of microwave (mw) pretreatment were quantified, providing mea...

With the aim to control and improve the thermo-chemical conversion of straw pellets, the experimental investigations of the DC electric field effect on the combustion dynamics and heat energy production were made. The electric field effect on the gasification/combustion characteristics was studied using three different positions of the positively c...

The main goal of the present study is to promote a more effective use of agriculture residues (straw) as an alternative renewable fuel for cleaner energy production with reduced greenhouse gas emissions. With the aim to improve the main combustion characteristics at thermo-chemical conversion of wheat straw, complex experimental study and mathematic...

The aim of this study was to provide more effective use of straw for energy production by co-firing wheat straw pellets with solid fuels (wood, peat pellets) under additional electric control of the combustion characteristics at thermo-chemical conversion of fuel mixtures. Effects of the DC electric field on the main combustion characteristics were...

The main goal of the present study is to assure a more effective use of CO2 neutral fuel (wheat straw) for cleaner energy production with reduced greenhouse carbon emissions by partially replacing a fossil fuel (crashed coal) with a renewable one. This work combines experimental study and mathematical modelling of the processes developing during th...

The main goal of the present study is to obtain a more effective utilization of wheat straw for energy production during a co-combustion with peat. For this purpose, an electric field was applied to the flame produced by the combustion of volatiles. This work combines experimental study and mathematical modelling of the processes developing during...

Thermo-chemical conversion of microwave activated wheat straw mixtures with wood or peat pellets is studied experimentally with the aim to provide more effective application of wheat straw for heat energy production. Microwave pre-processing of straw pellets is used to provide a partial decomposition of the main constituents of straw and to activat...

The main goal of this research is to promote a more efficient use of wheat straw for cleaner energy production by co-firing straw pellets with solid and gaseous fuels (wood pellets, propane) and to assess the impact of the mixture composition on the gasification/combustion characteristics and heat energy production. The effect of straw co-firing on...

Effects of wheat straw co-firing with gas (propane flame) and co-gasification/co-combustion with wood pellets on the development of thermo-chemical conversion of biomass pellets and on heat energy production were experimentally studied and analyzed with the aim to improve the gasification/combustion characteristics and the applicability of wheat st...

The development of the swirling flame flow field and gasification/ combustion dynamics at thermo-chemical conversion of biomass pellets has experimentally been studied using a pilot device, which combines a biomass gasifier and combustor by varying the inlet conditions of the fuel-air mixture into the combustor. Experimental modelling of the format...

Experimental studies and mathematical modelling of the effects of magnetic field on combustion dynamics at thermo-chemical conversion of biomass are carried out with the aim of providing control of the processes developing in the reaction zone of swirling flame. The joint research of the magnetic field effect on the combustion dynamics includes the...

Mathematical modelling and numerical simulation of second-order reaction kinetics for fast and slow exothermic reactions has been applied with the aim to estimate the development of composition and temperature profiles downstream of the flame reaction zone. The effects of slow and fast exothermic reactions on the formation of the flame composition...

Experimental study and mathematical modelling were aimed to provide electric control of biomass thermochemical conversion and analysis of the DC electric and electromagnetic effects on combustion dynamics to obtain a cleaner and a more effective heat energy production. Mathematical modelling of the formation of flame velocity and temperature profil...

Electric field effects (EFE) on combustion characteristics, heat energy production and composition of polluting emissions have been investigated experimentally for different types of fuels (natural gas, biomass) providing experimental study of the EFE in a district heating boiler (DKVR) and complex modelling experiments in a small-scale pilot devic...

With the aim to provide control of biomass thermal decomposition and combustion of volatiles, the external electric field effect on the wood biomass gasification/combustion characteristics during biomass thermo-chemical conversion at different stages of the swirling flame formation and heat energy production was experimentally studied.The DC electr...

An experimental was conducted with the aim to provide magnetic field control of the gasification / combustion characteristics and heat energy production at thermo-chemical conversion of biomass (wood) pellets. The results show that the gradient magnetic field - enchanced mass transfer of paramagnetic oxygen can be used as a tool to provide control...

Experimental investigations of the DC electric field effect on thermal decomposition of biomass, formation of the axial flow of volatiles (CO, H2, CxHy), mixing of volatiles with swirling airflow at low swirl intensity (S ≈ 0.2-0.35), their ignition and on formation of combustion dynamics are carried out with the aim to understand the mechanism of...

The effects of DC and AC electric field at 50 Hz and 13.56 MHz and 41 MHz frequencies on the combustion characteristics of biomass pellets have been investigated using an experimental setup of average power 20-40 kW with continuous pellet feed into the setup at average rates 1.5-3 g/s by applying AC voltage to the flame base, where thermal decompos...

The main aim of the present study is to obtain clean and effective heat energy production by applying a DC electric field to the flame reaction zone and providing control of the processes developing at thermochemical conversion of biomass (wood) pellets. The average heat power of the experimental device with continuous supply of pellets at an avera...

The aim of this study is to investigate the DC electric field effect on biomass gasification to provide effective control of processes developing at thermal decomposition of pelletized renewable fuels under oxygen rich conditions (a ≈ 0.06-0.12) and controllable production of combustible volatiles (CO, H2), which can be used as a fuel for energy pr...

Development of the swirling flame dynamics at thermo chemical conversion of biomass (wood pellets) has been investigated experimentally at a low swirl number of the swirling flame flow (S < 0.6) different rates of biomass thermal decomposition and swirling air supply with the aim to estimate key factors determining the formation of the flame dynami...

An experimental study was conducted by applying a DC electric field to the swirling flame of hydrocarbons with the aim to provide electric control of the gasification/combustion characteristics of biomass (wood pellets). An experimental study of the DC electric field effect on the biomass gasification/combustion characteristics was carried out by v...

The effect of swirling air on the flow dynamics was investigated for the cold non-reacting flows and the flame arising at thermo-chemical conversion of biomass pellets downstream of a cylindrical channel. Under experimental and numerical investigation was the swirling flow dynamics with the primary axial air supply below a biomass layer and swirlin...

An experimental study of the electric field effect on combustion dynamics at thermo-chemical conversion of biomass pellets was carried out with the aim to determine the DC field effect on the processes of biomass gasification, combustion of volatiles, formation of swirling flame structure, efficiency of heat energy production and composition of pol...

The main aim of this paper is improvement of the combustion characteristics of different biomass types (wood and agriculture residues, herbaceous biomass) by adding birch outer bark or bark (up to 20 %) to raw biomass with densification of the produced mixture. Produced pellets are experimentally characterized by elemental analysis determining the...

To effectively produce clean heat energy from biomass, microwave (mw) pre-processing of its different types - pelletized wood (spruce), herbaceous biomass (reed canary grass) and their mixture (50:50) - was carried out at the 2.45 GHz frequency with different durations of biomass exposure to high-frequency oscillations. To estimate the mw pre-proce...

The paper presents the results of an experimental study of the effect of high-frequency electromagnetic (EM) field oscillations on combustion and emission characteristics of biomass pellets with the aim to provide active control of the processes of biomass gasification and combustion. The effects of high frequency oscillations on the combustion cha...

Combustion characteristics of microwave (2.45 GHz) pre-treated biomass (wood) pellets are investigated experimentally with the aim to find out the effect of pellets pre-treatment on the biomass composition and the feasibility of their thermo-chemical conversion. A complex study of the main combustion characteristics of the pre-treated biomass sampl...